In power and free conveyor systems wherein carriers are moved along predetermined paths by engagement with conveyors, it is often necessary to transfer the carriers from one predetermined path to another. In one type of system, this transfer is achieved by providing a transfer conveyor that engages the carrier and transfers it between the predetermined paths. In another type of system, the carrier is moved from one path toward the other and then pushed through the transfer area to the second path.
The invention is also applicable to the transfer of a carrier from one powered conveyor to another, either from a faster to a slower conveyor or from a slower conveyor to a faster conveyor or between conveyors moving at the same speed.
In U.S. Pat. Nos. 3,640,226, and 3,662,873, there is shown a power and free conveyor system wherein each of the carriers has a second dog that is normally urged to operative carrier position but is held by the track out of operative position. At a transfer point, a portion of the track is cut away to permit the second dog to move to operative carrier transferring position. Such a system effectively provides for transfer of the carrier without any change in elevation of the power and free tracks. However, where the pushers on the conveyor chain are spaced apart greater distances or where the system includes transfer across short and long distances, a loss of efficiency in transfer may occur either because of the time delay in awaiting a pusher on the conveyor chain or minimum length between the first and second dogs.
It has also been heretofore suggested to provide a third dog on the carrier which has the same configuration as the second dog and is normally held out of operative position by the track but can be brought to operative position to transfer the carrier across a greater distance.
Among the objects of the present invention are to provide a power and free conveyor system wherein a carrier is transferred from one predetermined path to another by pushing across a transfer zone in a minimum period of time and wherein such system is achieved with minimum cost and maintenance; and wherein selective transfer of the carrier can be achieved over short and long distances as desired.